1. Field of the Invention
The present invention generally relates to a semiconductor structure and a method for making the semiconductor structure. In particular, the present invention is directed to a semiconductor structure with a complete lightly doped drain region which is sandwiched between a cap layer and a doped epitaxial material and a method for making the semiconductor structure to improve the reliability of the semiconductor structure.
2. Description of the Prior Art
In order to increase the carrier mobility of a semiconductor element, an advanced approach applies a stress to a gate channel. For example, an optional compressive or tensile stress may be applied to the gate channel. When it comes to a compressive stress which is required to be applied to the gate channel, the use of a SiGe epitaxial material is a popular fashion. A suitable compressive stress is generated towards the gate channel by means of larger germanium atoms in the SiGe epitaxial material.
It is also known that the stress is more effectively delivered to the gate channel of a semiconductor element and to adjust the carrier mobility when the stress source is closer to the gate channel so a recess is usually constructed adjacent to the gate structure, preferably with a collaterally formed tip deeply penetrating the gate channel, to deliberately deliver the stress to the gate channel. However, the reliability of the semiconductor structure would be susceptible to such approach.
Accordingly, a novel semiconductor structure is still needed to exhibit a better reliability.